Journal of Environmental Sciences - Volume 16, issue 6

Authors: WANG, Yu-jun | ZHOU, Dong-mei | LUO, Xiao-san | SUN, Rui-juan | CHEN, Huai-man

Article Type: Research Article

Abstract: Behaviors of soil heavy metals are often affected by coexisting herbicides due to their physical and chemical interaction. Effect of glyphosate, an herbicide containing -PO_3^{2-} and -COOH groups, on cadmium adsorption in montmorillonite was studied in detail. The results showed that cadmium adsorption quantity in montmorillonite increased with increasing soil solution pH and cadmium concentration as usual, but decreased with glyphosate, which is due to the formation of a low affinity …complex of Cd and glyphosate and decreasing solution pH induced by glyphosate addition. When the equilibrium solution pH was below 6.7, glyphosate has little effect on cadmium adsorption, but when the equilibrium solution pH was above 6.7, glyphosate significantly decreased cadmium adsorption quantity in montmorillonite. In addition, the adding order of Cd and glyphosate also influenced Cd adsorption quantity in montmorillonite. Show more

Keywords: cadmium, interaction, glyphosate, montmorillonite

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 881-884, 2004

Authors: LIU, Feng | LIU, Jian-guo | YU, Qian-feng | NIE, Yong-feng

Article Type: Research Article

Abstract: Chemical speciation is a significant factor that governs the toxicity and mobility of heavy metals in municipal solid waste incinerator fly ash. Sequential extraction procedure is applied to fractionate heavy metals (Pb, Zn, Cd, Cu, and Cr) into five defined groups: exchangeable, carbonate, Fe-Mn oxide, organic, and residual fractions. The mobility of heavy metals is also investigated with the aid of toxicity characteristic leaching procedure. In the fly ash sample, Pb is primarily presented in the …carbonate (51%) and exchangeable (20%) fractions; Cd and Zn mainly exist as the exchangeable (83% and 49% respectively); Cu is mostly contained in the last three fractions (totally 87%); and Cr is mainly contained in the residual fraction (62%). Pb, Zn and Cd showed the high mobility in the investigation, thus might be of risk to the natural environment when municipal solid waste incinerator fly ash is landfilled or reutilized. Show more

Keywords: municipal solid waste incinerator fly ash, heavy metals, chemical speciation, mobility

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 885-888, 2004

Authors: ZENG, De-wen | Born, Manfred | Wambach, Karsten

Article Type: Research Article

Abstract: The basic pyrolysis behaviour of ethylene vinyl acetate (EVA) copolymer, which is often used as a lamination agent in solar modules, was investigated in thermogravimetry, differential thermal analysis (DTA) and thermovolumetry. The TG analysis showed that the EVA pyrolysis can be accelerated under the partial oxidizing atmosphere but the end pyrolysis temperature must be higher than in nitrogen, to eliminate the coke formed. Meanwhile, a strong exothermal peak occurs at about 450°C under the air …condition and gets weaker obviously at the oxygen content lower than 10 vol.%. The mass balance of EVA pyrolysis was given through thermovolumetry with the output of 10 wt.% permanent gas, 89.9 wt.% condensate and 0.1% residual coke. Besides, the composition of the permanent gas and condensate at different pyrolysis stages were analysed and interpreted on the known pyrolysis mechanism. Show more

Keywords: pyrolysis, EVA, kinetic, recycling

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 889-893, 2004

Authors: CHENG, Jin-ping | ZHANG, Lan-ying | WANG, Wen-hua | YANG, Yi-chen | ZHENG, Min | JU, Su-wei

Article Type: Research Article

Abstract: A strain saccharomycete STSM-1 with high flocculanting activity was isolated from activated sludge with conventional methods. The high production rate and the low cost STSM-1 medium was obtained by selecting different kinds of media, carbon source, nitrogen source and inorganic salt ion. The best flocculant- producing conditions were found by changing medium initial pH, culture temperature and ventilation flow. The best flocculating effect was obtained by changing positive ion types, density and concentration of …flocculant. Show more

Keywords: microbial flocculants, flocculant-producing microorganisms, flocculating activity

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 894-897, 2004

Authors: ZHU, Guo-ying | LIU, Jun-xin

Article Type: Research Article

Abstract: The biofilter is cost-effective for the waste gases treatment. The bacterial is the main microorganism in the conventional biofilters. However, it faces some problems on the elimination of hydrophobic compounds. In order to overcome these problems, the biofilters with fungi were developed. The objective of this study is to investigate the factors affecting ethyl mercaptan (EM)-degradation using a fungal biofilter. A laboratory experiment was set up. The effects of loading rate, empty bed residence times (EBRT) …and pH on EM degradation were investigated. Over 95% removals of EM could be achieved, under the condition of the influent loadings below 50 g/ (m·h). Removal efficiencies improved to 98% with EM loading decreased to 45 g/(m·h). For long EBRT of 58 s corresponding to a flow rate of 0.3 m^3 /h, the EM removal efficiencies of over 98% were observed. However, when EBRT was decreased to 14 s, the removal efficiencies fell under 80%. The pH range of 3–5 was feasible to fungi. Show more

Keywords: off-gas treatment, odor, ethyl mercaptan, biofilter, fungi

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 898-900, 2004

Authors: MA, Yong | PENG, Yong-zhen | WANG, Shu-ying | WANG, Xiao-lian

Article Type: Research Article

Abstract: In order to improve nitrogen removal in anoxic/oxic (A/O) process effectively for treating domestic wastewaters, the influence factors, DO (dissolved oxygen), nitrate recirculation, sludge recycle, SRT (solids residence time), influent COD/TN and HRT(hydraulic retention time) were studied. Results indicated that it was possible to increase nitrogen removal by using corresponding control strategies, such as, adjusting the DO set point according to effluent ammonia concentration; manipulating nitrate recirculation flow according to nitrate concentration …at the end of anoxic zone. Based on the experiments results, a knowledge-based approach for supervision of the nitrogen removal problems was considered, and decision trees for diagnosing nitrification and denitrification problems were built and successfully applied to A/O process. Show more

Keywords: A/O process, nitrification, denitrification, nitrogen removal, decision trees

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 901-907, 2004

Authors: LUO, Lian-cong | QIN, Bo-qiang | ZHU, Guang-wei

Article Type: Research Article

Abstract: Investigation was made into sediment depth at 723 irregularly scattered measurement points which cover all the regions in Taihu Lake, China. The combination of successive correction scheme and geostatistical method was used to get all the values of recent sediment thickness at the 69 × 69 grids in the whole lake. The results showed that there is the significant difference in sediment depth between the eastern area and the western region, and most of the sediments …are located in the western shore-line and northern regimes but just a little in the center and eastern parts. The notable exception is the patch between the center and Xishan Island where the maximum sediment depth is more than 4.0 m. This sediment distribution pattern is more than likely related to the current circulation pattern induced by the prevailing wind-forcing in Taihu Lake. The numerical simulation of hydrodynamics can strong support the conclusion. Sediment effects on water quality was also studied and the results showed that the concentrations of TP, TN and SS in the western part are obviously larger than those in the eastern regime, which suggested that more nutrients can be released from thicker sediment areas. Show more

Keywords: objective analysis, geostatistics, sediment distribution, Taihu Lake

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 908-911, 2004

Authors: XIA, Yun-sheng | LI, Fang-bai | WAN, Hong-fu | MA, Jin | YANG, Guo-yi | LUO, Wei | ZHANG, Tian-bin

Article Type: Research Article

Abstract: Distribution and speciation of heavy metals of agricultural soils (85 surface soil samples and 4 soil profiles) in Dongguan were investigated, while total Cr, Cu, Ni, Pb, Zn (abbreviated as Cr, Cu, Ni, Pb, Zn) and available Cu, Zn (Av-Cu, Av-Zn) were analyzed by a flame absorption spectrophotometer (AAS), and total Cd (Cd) was analyzed using graphite furnace AAS. The content of Cd, Cu and Ni was partially much more than the second grade of GB15618-1995 even …though the mean contents of all heavy metal were less than the threshold value of the second grade and only the mean content of Pb was more than the value of national background. Results of descriptive statistic showed that the mean content of heavy metals should depend on land utilization and spatial location at some extent. The heavy metal contents were higher in the Southwest and Northwest than in the Central. In addition, the mean contents of Zn and Pb in Dongguan paddy soils were significantly higher than those of Pearl River Delta (PRD) and Taihu Lake region (TLR). Correlation analyses indicated that there existed significant correlation between Cr and Ni in orchard soils, and among Zn, Cd and Cu, between Av-Cu and Cu, between Av-Zn and Cr, Ni, pH value in vegetable soils, and a weak relationship between Cd, Cu and Pb, between Av-Zn and Zn. Principal component analyses (PCA) showed that the order of importance should be Zn> Pb> Cr> Ni> Cu. Show more

Keywords: heavy metal, spatial distribution, agricultural soil, Dongguan

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 912-918, 2004

Authors: WANG, Xue-jiang | ZHAO, Jian-fu | XIA, Si-qing | LI, Ai-min | CHEN, Ling

Article Type: Research Article

Abstract: The adsorption of two phenols, namely, phenol and salicylic acid (SA) onto a water-compatible hypercrosslinked polymeric resin (NJ-8) were studied in terms of pseudo-second-order and first order mechanisms for chemical sorption as well as an intraparticle diffusion mechanism process. Kinetic analysis showed that the intraparticle diffusion process was the essential rate-controlling step. The activation energies of sorption have also been evaluated with the pseudo-second-order and intraparticle diffusion constants, respectively. Adsorption equilibrium data …were well fitted by the Langmuir, Freundlich and Redlich-Peterson isotherms. Adsorption was exothermic and basically of a type of transition between physical and chemical character. The sorption capacity was higher for SA due to its more hydrophobic. Phenol has a higher adsorption enthalpy since it could form stronger hydrogen bonding on NJ-8. Show more

Keywords: hypercrosslinked polystyrene resin, phenol, salicylic acid (SA), adsorption, enthalpy

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 919-924, 2004

Authors: WEI, Hong | TONG, Shao-ping | WANG, Hong-yu | LIU, Wei-ping

Article Type: Research Article

Abstract: The utility of nickel/iron in the remediation of atrazine-contaminated water was investigated. The experimental results showed that nickel/iron had effective catalytic activity in dechlorinating atrazine under acidic conditions. The dechlorination reaction approximately followed the first-order kinetics under the experimental conditions (nickel/iron: 1.0 g/250 ml; C_{atrazine} =20.0 mg/L), the reaction rate increased with decreasing pH value of the reaction solution and increasing the proportion of Ni:Fe within 2.95%. For condition with 2.95% …nickel/iron, the reaction rate constants were 0.07518 (R=0.9927), 0.06212 (R=0.9846) and 0.00131 min^{-1} (R=0.9565) at pH=2.0, 3.0 and 4.0, respectively. HPLC analysis was used to monitor the decline of atrazine concentration. Show more

Keywords: atrazine, nickel/iron bimetallic system, dechlorination reaction, first-order kinetics

Citation: Journal of Environmental Sciences, vol. 16, no. 6, pp. 925-927, 2004